Permanent paper and method of making same



Patented Dec. 27, 1949 UNITED STATES. PATENT ornce PERMANENT PAPER AND METHOD OF MAKING SAME John Studeny, Erie, Pa., Jofhn D. Pollard, Baltimore, Md., and Chester G. Landes, New Canaan, Conn., assignors to American Cyanamid Company, New York, N. Y., a corporation of Maine No Drawing. Application September 28, 1948, Serial No. 51,654

5 Claims. (Cl.-117--154) This invention relates to paper and similar products composed of felted cellulosic fibers hav-. ing improved permanence and stability on storageand heating. The invention includes the improved paper and other felted cellulosic material and methods of producing the same.

It is a well-known fact that articles composed of or containing felted or molded cellulosic fibers felted fibrous articles containing acidic materials I and normally having a pH of about 4 to 6 will deteriorate faster upon storage or heating than those which are completely neutral. For this reason the aging characteristics, for example, of ordinary writing paper sized with rosin size and alum are not ordinarily as good as those of un sized or untreated papers. tage of the stabilizing agents of the present in} vention that they will retard the embrittlement and discoloration of paper containing small amounts of residual acid or of acidic materials.

Our invention is based on the discovery that ammonium and alkali metal salts of dicyanoguanidine are effective stabilizing agents to re- It is a further advam 2 point during :or after it is'formed on'a-papermaking machine; Since all of the stabilizing agents are water-soluble they can be incorporated into the paper very Simply by impregnation from water solution, and this can be done in conjunc- 'tion with sizing agents and the like during the finishing of the paper'if desired. Thus, for exam ple, water solutions of our stabilizing agents may be sprayed on the felted paper sheet, or they may be applied as a tub size; When a closed white water system isused, they may be addedto the paper stock suspension prior to formation of the sheet, and. may be used alongwith other beatersizing agents such as rosin size and alum, starch, glue, fillers, colors, resins and the like materials.

As is noted above, the minimum quantity of the stabilizing agents that will produce the desired result in paper are on the order of about 0.3%, based on the dry weight of the cellulose. For most purposes, satisfactory results are obtained when about 0.5% to about 5% of the sta bili'zing agent is used. Amounts of more than 10% usually produce no further advantages, and

therefore are not recommended.

The ammonium and alkali metal salts of di cyanoguanidine, any of which may be used in practicing the invention, are all soluble in water but are normally solid and colorless and there-- tard the deterioration of paper and other felted.

in character, they do not alter the appearance or affect the utility of the paper for its intended purpose.

In practicing the process of our invention the ammonium or-alkali metal salts of dicyanoguanidine may be added to the paper at any desired alkali metal or ammonium salts of dicyandiam'ide with cyanogen chloride. The preparation of these;

salts is disclosed with particularity in U. S. Patent No. 2371100.

The invention will be further illustrated by the following specific examples. It should be understood, however, that although these examples may describe in detail 'certain specific embodimentsv of the invention, they are given priimirily for purposes ofriillustration and the invention in its broader aspects is not limited theretob Example I A commercial sulfite bond paper was im pregnated with a water solution of the stabilizing agents'listed below'by immersing the paper in a1 physical methods. The results are given in the following table. In the headings of this table MD means machine direction, CD means cross direction and Refl. means reflectance measured 4 4. Paper containing about 0.3 per cent to per cent by weight of ammonium dicyanoguanidine. 5. A method of improving the stability of paper against aging which comprises impregnating said at 450 millimicrons on a G. E. recording spectro- 5 paper with an aqueous solution of a member sephotometer. lected from the group consisting of ammonium Unaged Paper Stabilizer Per Oent sh t M. I. T. Fold ee pH Refl.

MD CD None (control) 5.4 87 33 72 Potassium Dicyanoguanidine 5. 3 87 70 Sodium Dicyanogusnidine"- 5. 4 85 28 71 Aged Paper M. T. T. PercentFold Stabilizer Per Cent Fold Retention Sheet Refl D CD MD (JD None (control) 4. 9 22 67 40.2 66. 2 Potassium Dicyanoguanidine. 2 3 5. 5 70 24 64 80. 5 96 Sodium Dicyanoguanldine- 2 1 5. 6 69 24 64 75.3 85. 7

.lMeans the per cent of retention of stabilizer, based on the weight of the cellulose,

Example 2 A safety-check base paper having a relatively low pH was impregnated, dried, and tested as in Example 1 with the following results:

and alkali metal salts of dicyanoguanidine and subsequently drying the paper to retain therein about 0.3 per cent to 10 per cent of said compound.

Unaged Paper Stabilizer Per Cent M. I. T. Fold g Refl. MD CD None (control) 4. 0 36 Potassium Dicyanoguanidine. l. 6 4. 8 23 26 66 Ammonium Dicyanoguanidine.. 1. 4 4. 4 21 24 66 Aged Paper M. I. T. Percent Fold Stabilizer Per Cent Fold Retention Sheet Refl MD OD MD CD None (control) 3. 8 2 4 59 5. 7 10 Potassium Dicyanoguauidine 1. 6 5. 3 ll 23 59 47. 8 88. 4 Ammonium Dicyanoguanidine l. 4 5. 1 9 18 57 42. 8

'1 Means the per cent of retention of stabilizer, based on the weight of the cellulose.

What we claim is:

1. Paper containing about 0.3 per cent to 10 60 the paper is a normally acid paper having a pH 6 of' about 4 to 6.

3. Paper containing about 0.3 per cent to 10 per cent by weight of potassium dicyanoguanidine.

JOHN STUDENY. JOHN D. POLLARD. CHESTER G. LANDE'S.

REFERENCES CITED 5 The following references are of record in th Number Name Date Kaiser et a1 Mar. 6, 1945 

